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  1. Bug #131094
  2. Comment #202

Comment 202 for bug 131094

Revision history for this message
Jamie Lokier (jamie-shareable) wrote : Re: [Bug 131094] Re: Heavy Disk I/O harms desktop responsiveness

Milan wrote:
> Thanks for these detailed informations. So you suggest that the IO
> scheduler is not giving enough priority to tasks other than the file
> copy; that's an interesting way of finding the cause of the problem,
> indeed! I suggest you try the new kernel, and if it's not fixed, go to
> the upstream report and explain them your case. You can find many
> different scripts to test the system's responsiveness there, and you'll
> notice that's really tricky (long thread...).

I suggest it's not just about giving I/O priority to tasks other than
the copy, but also giving them enough "anticipatory" time so there
isn't a pair of head seeks for every I/O operation by the non-copying
tasks.

It has to look like this to be efficient:

    I/O for copy
    I/O for copy
    I/O for copy
    I/O for copy
    I/O for copy
                <head seeks>
                           I/O for other thing
                           I/O for other thing
                           I/O for other thing
                           I/O for other thing
                           I/O for other thing
                <head seeks>
    I/O for copy
    I/O for copy
    I/O for copy
    I/O for copy
    I/O for copy
                <head seeks>
                           I/O for other thing
                           I/O for other thing
                           I/O for other thing
                etc.

And not

    I/O for copy
                <head seeks>
                           I/O for other thing
                <head seeks>
    I/O for copy
                <head seeks>
                           I/O for other thing
                <head seeks>
    I/O for copy
                <head seeks>
                           I/O for other thing
                <head seeks>
                etc.